Prior to the present disclosure, methods were known for generating metal anion beams with high kinetic energies (e.g., kinetic energies in a range of 1-1000 keV). However, for numerous processes, it would be desirable to have access to low-energy gas-phase metal anions generated under mild conditions. As used herein, “mild” refers to conditions that do not impart a large excess of kinetic energy to the anion beyond the energy needed to produce it. In the field of mass spectrometry, processes operating under such conditions may also be referred to as “soft”, as opposed to “hard”, ionization processes. A practical reason for preferring mild (or “soft”) processes is that the ions formed from such processes often exhibit a different gas-phase chemistry than those produced under more energetic (or “hard”) processes. A method for efficiently generating low-kinetic-energy metal anion beams using bench-top laboratory equipment has potential applications for the production of nanoscale materials, for the production of reagent ions to induce chemical transformations in gas phase-microreactors, for surface analysis, for imaging science, for medical research, and for uses in other areas of science and engineering. For example, metal ion beams are essential for applications in the field of accelerator mass spectrometry for the analysis of rare isotopes and trace elements. Gas-phase anions with low electron affinities (e.g., alkali metal anions, or “alkalides”) also have important applications as electron transfer agents in an emerging technique for protein structure elucidation called electron transfer dissociation (ETD). The production of alkali metal anions is also a required first step for some nuclear physics research experiments.